Others complained of seeing a double up in mortgage payments or insurance payments go out on Friday.
Another couple got a shock to see their first mortgage payment go out twice.
In a statement on its Facebook page, Westpac New Zealand said some customers were experiencing missing or duplicated transactions on their Westpac One timelines.
A Westpac spokesman could not immediately say how many customers were affected.
Some customers said they were happy that Westpac were onto the error although they would like to have seen communication sooner from the bank.